The present invention relates to plating baths or plating metal onto substrates. More particularly, she present invention relates to an apparatus and method for monitoring and adjusting conditions within plating baths and for plating metal onto substrates.
Baths or reservoirs for holding a plating bath that includes at least one material, such as a metal, to be, plated on a substrate are used in a wide variety of applications. For example, plating baths are commonly used in microelectronic device manufacturing. According to one example, baths are utilized for electroplating and for electroless plating on substrates.
Composition of plating baths and conditions within the plating bath must be carefully controlled to produce deposition of a desired quality of desired metal(s) on a substrate. Plating rate, uniformity, and deposit quality may be affected by a variety of factors. For example, one parameter that may affect rate, uniformity, and deposit quality of plating is concentration of chemicals in the plating bath as well as uniform distribution of the chemicals during production.
Along these lines, it is desirable to maintain the plating bath solution as close as possible to ideal conditions for plating. However, as the plating process proceeds, the characteristics of the solution, such as concentration and uniformity of chemicals, change as chemicals are used up in the plating process and components of the plating bath, such as surfactants, break down chemically and various byproducts build up.
According to standard practice, materials making up the plating bath typically are added individually directly to the bath. Once material is added to the bath, a period of time must pass before the material will be uniformly distributed throughout the plating bath. As can be appreciated, differential concentration of a material in the plating bath can with time result in non-uniform amounts plating distribution and variable deposit quality. For example, the quality of films plated relatively later may be interior to the quality of earlier plated films.
An object of the present invention is to provide a system for pre-mixing chemicals to be added to a plating bath.
Another object of the present invention is to provide an apparatus and method for helping to ensure uniform distribution of materials in a plating bath.
An additional object of the present invention is to provide a method and apparatus for helping to ensure uniform plating of a material on a substrate.
A further object of the present invention is to provide an apparatus and method for monitoring a plating bath and adding materials as required.
Yet another object of the present invention is to provide an apparatus and method for controlling the quality of deposited metal.
Still another object of the present invention is to provide an apparatus and method for recycling and recovering plating solutions in situ.
In accordance with these and other objects and advantages, the aspects of the present invention provide an apparatus for monitoring and adding materials to a plating bath. The apparatus includes at least one monitor for monitoring conditions within the plating bath and producing at least one signal corresponding to the monitored conditions. At least one controller receives the at least one signal produced by the at least one monitor, processes the at least one signal, determines whether an additional amount of at least one chemical should be added to the plating bath, and controls at least one valve for controlling flow of the at least one chemical. A pre-mix tank is provided for pre-mixing chemicals to be added to the plating bath. A plurality of holding tanks hold chemicals and supply chemicals to the pre-mix tank. A valve is provided between each of the holding tanks and the pre-mix tank, as well as between the pre-mix tank and the plating bath.
Aspects of the present invention also provide a plating bath system including a plating bath reservoir for holding a plating bath and plating at least one material from the plating bath onto at least one substrate. At least one monitor monitors conditions within the plating bath and produces at least one signal corresponding to the monitored conditions. At least one controller receives the at least one signal produced by the at east one monitor, processes the at least one signal, determines whether an additional amount of at least one chemical should be added to the plating bath, and controls at least one valve for controlling flow for the addition of the additional amount of the at least one chemical. A pre-mix tank is provided for pre-mixing chemicals to be added to the plating bath. A plurality of holding tanks holds chemicals and supplies the chemicals to the pre-mix tank. At least one valve is provided between each of the holding tanks and the pre-mix tank, as well as between the pre-mix tank and the plating bath. The method includes introducing at least one treatment chemical into each holding tank. Selected ones of the treatment chemicals are introduced into the pre-mix chamber. The selected ones of the treatment chemicals are introduced into the plating bath reservoir to act as a plating bath after passage of a period of time sufficient for the selected ones of the treatment chemicals to mix in the pre-mix chamber. At least one substrate to be treated is introduced into the plating bath. At least one condition within the plating bath is monitored by the at least one monitor. The at least one monitored condition is analyzed to determine whether the plating bath requires addition of at least one treatment chemical. The valves of the plating bath system are controlled with the processor to introduce a required additional amount at least one treatment chemical into the pre-mix chamber from at least one of the holding tanks. The additional amount of at least one treatment chemical is introduced into the plating bath reservoir after passage of a period of time sufficient for the added treatment chemicals to mix.
Furthermore, aspects of the present invention provide a method for controlling a plating bath solution in a plating bath system that includes a plating bath reservoir, at least one monitor, at least one controller, a pre-mix tank, a plurality to holding tanks, at least one valve between each of the holding tanks and the pre-mix chamber and at least one valve between the pre-mix tank and the plating bath reservoir. The method includes monitoring at least one condition within the plating bath with the at least one monitor. The at least one monitored condition is analyzed to determine whether the plating bath requires addition of at least one treatment chemical. The valves in the plating bath system are controlled for introducing the required additional amount at lease one treatment chemical into the pre-mix tank from at least one of the holding tanks. The additional amount of at least one treatment chemical is introduced into the plating bath reservoir after passage of a period of time sufficient for the additional at least one treatment chemical to mix.